Dietary lipid composition affects blood leucocyte fatty acid compositions and plasma eicosanoid concentrations in European sea bass (Dicentrarchus labrax)

Broodstock European sea bass were fed three dry pelleted feeds for 12 month s prior to the onset of spawning. The diets contained (a) Northern hemisphe re fish meal and oil (control), (b) krill meal and Northern hemisphere fish oil (krill), or (c) Northern hemisphere fish meal and tuna orbital oil (Ro PUFA). The RoPUFA diet contained more docosahexaenoic acid (22:6n - 3; DHA) (60%), less eicosapentaenoic acid (20:5n - 3; EPA) (20%) and more arachido nic acid (20:4n - 6; AA) (two-fold) compared to the other two diets. The to tal lipid fatty acid composition of purified blood leucocytes broadly refle cted the dietary fatty acid input, with respect to the three long-chain hig hly unsaturated fatty acids (HUFA) described above, although DHA levels wer e only slightly elevated in the fish fed RoPUFA. The fatty acid composition s of the major phospholipid classes of blood leucocytes, phosphatidylcholin e (PC), phosphatidylethanolamine (PE), phosphatidylserine (PS) and phosphat idylinositol (PI), were measured. In all phospholipid classes, the 22:6n - 3 level was relatively constant for all dietary treatments suggesting that dietary 22:6n - 3 concentrations were adequate in all diets. By contrast, t he apparent demand for AA was not met by the control and krill diets while the moderately increased AA present in the RoPUFA diet was rapidly and effi ciently incorporated into cellular lipids. The percentages of 20:4n - 6 var ied in accordance with dietary input with highest levels in leucocytes from fish fed RoPUFA followed by those fed the krill diet and lowest values in control fish. Percentages of 20:5n - 3 were also influenced by diet with th e highest levels found in fish fed the krill diet and the lowest in fish fe d RoPUFA. Thromboxane B-2 (TXB2) and TXB3 derived from AA and EPA, respecti vely, were measured in plasma. In all dietary treatments. more TXB2 than TX B3 were produced with the highest values of the former found in fish fed Ro PUFA. Leukotriene B-4 (LTB4) and LTB5 derived from AA and EPA, respectively , were also measured in plasma but no significant differences were found be tween dietary treatments. (C) 1999 Elsevier Science B.V. All rights reserve d.